Series-connected battery packs, system and method

ABSTRACT

A power device including a housing, charging circuitry, and discharge circuitry. The housing defining a first support operable to support a first battery pack, and a second support operable to support a second battery pack. The charging circuitry electrically is connected to the first battery pack and the second battery pack in a parallel-type connection. The charging circuitry is configured to simultaneously charge the first battery pack and the second battery pack. The discharge circuitry is electrically connected to the first battery pack and the second battery pack. The discharge circuitry is configured to electrically connect the first battery pack and the second battery pack in a series-type connection during a discharge

RELATED APPLICATION

The present application claims priority to U.S. patent application Ser.No. 15/603,862, filed May 24, 2017, now U.S. Pat. No. 10,483,791, whichclaims priority to U.S. Provisional Application No. 62/341,397, filedMay 25, 2016, the entire contents of both of which are herebyincorporated by reference.

FIELD

The present invention relates to battery power sources andbattery-powered devices and, more particularly, to series-connectedbattery packs in such power sources and devices.

SUMMARY

To provide a desired operating voltage, two or more battery packs may beconnected in series. When connected in series, the voltage of each packis added to a total terminal voltage of the system. However, operationof series-connected battery packs is generally limited by the packhaving the lowest capacity.

For battery packs including lithium-based battery cells, discharge ofseries-connected packs is stopped when one of the packs is disabled, forexample, because the pack has reached an end of discharge condition(e.g., state of charge (SOC) below a threshold), is experiencing anabnormal condition (e.g., excessive temperature, cell voltage drop,etc.). This requirement presents challenges with series-connectedbattery packs, especially with packs having different capacities,different states of charge, etc. When one pack reaches its end ofdischarge condition, the other battery pack(s) will have remainingcapacity that will not be harnessed by the system.

In some aspects, one or more solutions to maximize the discharge energyof series-connected battery packs in a system may be provided. In someaspects, an ability to mix and match packs with different capacities,different states of charge, different nominal voltages, etc. in thesystem may be provided.

In some embodiments, the system may be controlled to work at less thanfull capacity of battery packs. For example, a proportional dischargeenergy may be drawn from each pack based upon the capacity/condition ofthe pack so that the packs reach end of discharge substantiallysimultaneously. In another example, the pack at its end of discharge maybe disconnected from the circuit, after which operation of the system iscontinued through to end of discharge of all series-connected packs inthe system.

In some embodiments, the system may provide a charge platform so that,during charging, each battery pack is brought to substantially the samestate of charge. For example, the platform may provide a seriesconnection between the battery packs during discharge, and, duringcharging, each battery pack may be connected independently or in aparallel connection to a power source. The charge platform may notaddress different capacities between the battery packs.

In one independent aspect, a battery power device may generally includea housing defining a first support operable to support a first batterypack, and a second support operable to support a second battery pack; acircuit selectively electrically connecting the first battery pack andthe second battery pack in series, the circuit including an outputterminal to provide an output voltage to a powered device, a firstbypass portion operable to selectively electrically disconnect the firstbattery pack from the circuit, and a second bypass portion operable toselectively electrically disconnect the second battery pack from thecircuit; and a boost converter electrically connected to the circuit andoperable to boost a voltage at the output terminal.

In some embodiments, the boost converter is selectively electricallyconnected in series with the first battery pack and the second batterypack, the boost converter being operable to boost a first voltage of thefirst battery pack and a second voltage of the second battery pack tothe output voltage.

The first battery pack may have a first nominal voltage, and the secondbattery pack may have a second nominal voltage different than the firstnominal voltage. The first battery pack may have a first capacity, andthe second battery pack may have a second capacity different than thefirst capacity. The first battery pack may have a first state of charge,and the second battery pack may have a second state of charge differentthan the first state of charge.

In another independent aspect, a power system may generally include afirst battery pack; a second battery pack; and a battery power deviceoperable to provide an output voltage to a powered device. The batterypower device may generally include a housing defining a first supportoperable to support the first battery pack, and a second supportoperable to support the second battery pack, a circuit selectivelyelectrically connecting the first battery pack and the second batterypack in series, the circuit including an output terminal to provide theoutput voltage to the powered device, a first bypass portion operable toselectively electrically disconnect the first battery pack from thecircuit, and a second bypass portion operable to selectivelyelectrically disconnect the second battery pack from the circuit, and aboost converter electrically connected to the circuit and operable toboost a voltage at the output terminal.

In yet another independent aspect, a method of powering a powered devicemay generally include selectively electrically connecting a firstbattery pack and a second battery pack in a circuit in series; providingan output voltage at an output terminal; boosting a voltage at theoutput terminal; and, when one of the first battery pack and the secondbattery pack reaches an end of discharge condition, selectivelyelectrically disconnecting the one of the first battery pack and thesecond battery pack from the circuit.

In some embodiments, boosting may include selectively electricallyconnecting a boost converter in series with the first battery pack andthe second battery pack, and operating the boost converter to boost afirst voltage of the first battery pack and a second voltage of thesecond battery pack to the output voltage. Selectively electricallyconnecting may include selectively electrically connecting in thecircuit in series a first battery pack having one of a first nominalvoltage, a first capacity, and a first state of charge and with a secondbattery pack having a corresponding one of a second nominal voltage, asecond capacity, and a second state of charge different than the first.

The method may include removably connecting the first battery pack to ahousing of the device and/or removably connecting the second batterypack to the housing of the device.

Selectively electrically disconnecting may include determiningcharacteristics or condition of the first battery pack, and controllingoperation of a bypass portion. When the first battery pack is to bedisabled, controlling may include disconnecting the first battery packfrom the circuit. When another battery pack is substituted for adisabled first battery pack, controlling may include determining whetherto control the bypass portion to connect the other battery pack to thecircuit.

The method may include determining an input voltage of the powereddevice, and wherein boosting includes boosting the voltage at the outputterminal to the input voltage.

In a further independent aspect, a battery power device may generallyinclude a housing assembly defining a first support operable to supporta first battery pack, and a second support operable to support a secondbattery pack; a discharge circuit including an output terminal toprovide an output voltage to a powered device and selectivelyelectrically connecting the first battery pack and the second batterypack in series for discharging; and charging circuitry including aninput terminal to receive power from a power source and selectivelyelectrically connecting the first battery pack and the second batterypack to the power source for charging.

A switch arrangement may be provided to selectively and alternativelyelectrically connect the first battery pack and the second battery packto the discharge circuit and to the charging circuitry. The device mayinclude a controller operable to control the switch arrangement based ona signal indicative of a connection status of one of the output terminaland the input terminal. The switch arrangement may include an actuatoroperable by a user.

In some constructions, the housing assembly includes a removable carrierportion providing the first support and the second support, the chargingcircuitry being supported by the removable carrier portion.

For charging, the battery packs may be connected in parallel by thecharging circuitry. The battery packs may be independently charged bythe charging circuitry. During a charging cycle, the battery packs maybe charged by the charging circuitry to approximately the samestate-of-charge and/or to approximately the same capacity.

In another independent aspect, a battery power device may generallyinclude a housing defining a first support operable to support a firstbattery pack, and a second support operable to support a second batterypack; a discharge circuit selectively connecting the first 0battery packand the second battery pack in series, the discharge circuit includingan output terminal to provide an output voltage to a powered device; anda balance circuit selectively connected to the first battery pack andthe second battery pack, the balance circuit being operable to transferenergy between the first battery pack and the second battery pack.

The device may include a controller operable to control operation of thebalance circuit. The controller may be operable to determine a non-usecondition of the discharge circuit, and operate the balance circuitduring the non-use condition.

In yet another independent aspect, a battery power device may be usedwith a multi-phase motor and may generally include a housing defining afirst support operable to support a first battery pack, a second supportoperable to support a second battery pack; a first switch arrangementbetween the first battery pack and the motor; and a second switcharrangement between the second battery pack and the motor, the firstswitch arrangement and the second switch arrangement being operable toselectively connected the first battery pack and the second battery packacross each phase of the motor, the first switch arrangement and thesecond switch arrangement being operated to provide the required energyfrom at least one of the first battery pack and the second battery packto each phase of the motor.

In another independent aspect, a power device includes a housing andcharging circuitry. The housing defining a first support operable tosupport a first battery pack, and a second support operable to support asecond battery pack. The charging circuitry electrically is connected tothe first battery pack and the second battery pack in a parallel-typeconnection. The charging circuitry is configured to simultaneouslycharge the first battery pack and the second battery pack.

In yet another independent aspect, a method of operating a power deviceincludes receiving, via a first support, a first battery pack, andreceiving, via a second support, a second battery pack. The methodfurther includes electrically connecting the first battery pack to acharging circuitry in a parallel-type electrical connection,electrically connecting the second battery pack to the chargingcircuitry in a parallel-type electrical connection. The method furtherincludes simultaneously charging, via the charging circuitry, the firstbattery pack and the second battery pack.

Other independent aspects of the invention may become apparent byconsideration of the detailed description, claims and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a power system includingserially-connected battery packs.

FIG. 2 is a schematic view of a portion of the system shown in FIG. 1.

FIG. 3 is a schematic view of charging circuit for a power system, suchas the system of FIG. 1.

FIG. 4 is a schematic view of a balancing circuit for a power system,such as the system of FIG. 1.

FIG. 5 is a schematic view of a matrix converter of a power system.

FIG. 6 is a schematic view of an inverter/bridge of the matrix convertershown in FIG. 5.

DETAILED DESCRIPTION

Before any independent embodiments of the invention are explained indetail, it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description or illustrated in thefollowing drawings. The invention is capable of other independentembodiments and of being practiced or of being carried out in variousways. Also, it is to be understood that the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting.

Use of “including” and “comprising” and variations thereof as usedherein is meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Use of “consisting of” andvariations thereof as used herein is meant to encompass only the itemslisted thereafter and equivalents thereof.

FIGS. 1-2 illustrate a battery power system 10 including a battery powerdevice 14 supporting and electrically connecting a number of separatebattery packs 18 a, 18 b . . . 18 n in series and operable to provide anoutput voltage to a powered device 22. The system 10 is operable as apower source for various heavy-duty, high-voltage devices, includingpower tools similar to corded AC power tools, such as miter saws,planers, band saws, diamond coring motors, drills, grinders, magneticdrill presses, rotary and demolition hammers, compressors, etc., outdoorpower equipment, such as string trimmers, blowers, hedge trimmers, lawnmowers, chain saws, pressure washers, wood chippers, snow blowers, etc.The system 10 may be constructed with an output or an auxiliary outputand be operable to provide power in a manner similar to a generator.

The device 14 includes a housing assembly 26 defining a number ofbattery pack bays or support portions 30 a, 30 b . . . 30 n, eachoperable to support a battery pack 18. The device 14 includes a circuit34 supported by the housing assembly 26 and operable to selectivelyconnect the supported battery packs 18 in series. The circuit 34includes, for each support portion 30, (see FIG. 2) a circuit portion 38with terminals 42 operable to electrically connect to terminals 46 ofthe supported battery pack 18. The circuit 34 includes (see FIG. 1)output terminals 50 electrically connectable to the powered device 22(e.g., a motor/drive of a power tool (e.g., the motor 90 (see FIG. 5), amachine, etc.) to provide an output voltage to the powered device 22.

A boost converter 54 is electrically connected to the circuit 34 andoperable to boost a voltage across the output terminals 50. In theillustrated construction, the boost converter 54 is selectivelyconnected in the circuit 34 in series with the circuit portions 38. Theboost converter 54 is operable to boost the voltage of the batterypack(s) 18 to the output voltage.

In the illustrated construction, the boost converter 54 boosts the inputvoltage of the supported battery pack(s) 18 to a set or desired outputvoltage (e.g., 120V, 240 V, 400 V, etc.). Regardless of the inputvoltage to the circuit 34 (e.g., number of supported battery packs 18,state-of-charge of the supported battery pack(s) 18, nominal voltage ofthe supported battery pack(s) 18, etc.), the output voltage of thedevice 14 is the same—the set output voltage provided by the boostconverter 54. Because the output voltage covers a wide range of commonvoltages used worldwide (e.g., 110 V to 240 V), the device 14 mayprovide a universal power source.

In other constructions (not shown), the boost converter 54 may beprovided by distributed boost converters (not shown; e.g., a boostconverter being provided for each circuit portion 38). In suchconstructions, each separate boost converter is operable to boost thevoltage of an associated supported battery pack 18 to a set or desiredvoltage for the battery pack 18.

A controller 58 is electrically connected to the circuit 34 and isoperable to configure, communicate with and/or control the system 10 andcomponents of/connected to the system 10. In the illustratedconstruction, the controller 58 is operable to determine characteristicsand/or conditions of the battery pack(s) 18 connected to the circuit 34.In the illustrated construction, each battery pack 18 includes (see FIG.2) a pack controller 62, and the controller 58 is operable tocommunicate with each pack controller 62 to determine characteristics(e.g., nominal voltage, capacity, cell chemistry, etc.) and/orconditions (e.g., state-of-charge, temperature, etc.) of the associatedbattery pack 18.

The controller 58 (and the controller(s) 62) includes combinations ofhardware and software. The controller 58 includes a processing unit(e.g., a microprocessor, a microcontroller, or another suitableprogrammable device), non-transitory computer-readable media, and aninput/output interface. The processing unit, the media, and theinput/output interface are connected by one or more control and/or databuses. The computer-readable media stores program instructions and data.The processing unit is configured to retrieve instructions from themedia and execute the instructions to perform the control processes andmethods described herein.

The input/output interface transmits data from the controller 58 toexternal systems, networks, and/or devices and receives data fromexternal systems, networks, and/or devices. The input/output interfacestores data received from external sources to the media and/or providesthe data to the processing unit.

The circuit 34 includes a bypass portion 66 a, 66 b . . . 66 n operableto selectively disconnect each associated supported battery pack 18 a,18 b . . . 18 n from the circuit 34. In the illustrated construction,when it is determined that a battery pack 18 a, 18 b . . . 18 n is to bedisabled (e.g., has reached an end of discharge threshold, isexperiencing an abnormal condition, etc.), the controller 58 controlsthe associated bypass portion 66 a, 66 b . . . 66 n to disconnect thebattery pack 18 a, 18 b . . . 18 n from the circuit 34. After thedisabled battery pack is disconnected, operation of the system 10 isable to continue through to end of discharge of all remainingseries-connected packs 18 a, 18 b . . . 18 n in the system 10.

Each bypass portion 66 a, 66 b . . . 66 n may include one or moreswitches, such as, for example, a XOR switches, operable so that theassociated battery pack 18 a, 18 b . . . 18 n is normally connected inseries in the circuit 34 (a “connected” condition) and is disconnectedwhen the battery pack 18 a, 18 b . . . 18 n is disabled (a“disconnected” condition). This arrangement forms a “smart cell” so thatthe associated battery pack 18 a, 18 b . . . 18 n is either put in thecircuit 34 or bypassed. The battery packs 18 a, 18 b . . . 18 n may beswitched into and out of the circuit 34 based on disabling of thebattery pack 18 a, 18 b . . . 18 n (e.g., SOC, temperature, etc.) Thisarrangement allows all battery packs 18 a, 18 b . . . 18 n in the system10 to be completely discharged.

If a battery pack 18 a, 18 b . . . 18 n is disconnected from the circuit34 before end of discharge (e.g., due to an abnormal condition), thecontroller 58 may control the associated bypass portion 66 a, 66 b . . .66 n to again connect the battery pack 18 a, 18 b . . . 18 n to thecircuit 34 if it is determined that the condition has been removed andthe battery pack 18 a, 18 b . . . 18 n is operational.

If another battery pack (not shown) is substituted for a disconnectedbattery pack 18 a, 18 b . . . 18 n, the substituted battery pack may beconnected to the circuit 34. For example, the controller 58 maycommunicate with the substituted battery pack (e.g., with its batterypack controller (not shown)) to determine whether the battery pack isoperational (not disabled due to SOC, an abnormal condition, etc.) and,if the battery pack is determined to be operational, control theassociated bypass portion 66 a, 66 b . . . 66 n to connect thesubstituted battery pack to the circuit 34.

Alternatively, when a battery pack 18 a, 18 b . . . 18 n is removed fromits support portion 30 a, 30 b . . . 30 n, the associated bypass portion66 a, 66 b . . . 66 n may reset to the connected condition. Duringsubsequent operation, the associated bypass portion 66 a, 66 b . . . 66n would then be controlled as described above based on the condition ofthe substituted battery pack.

The controller 58 is electrically connected to the boost converter 54and is operable to communicate with and control the boost converter 54.The boost converter 54 can be controlled to boost the input voltage (ofthe battery pack(s) battery pack 18 a, 18 b . . . 18 n) as necessarybased on the load of the powered device 22.

The powered device 22 may also include a controller (not shown)communicating with the controller 58. The powered device controller maycommunicate information relating to the powered device 22 (e.g., theload, a desired input voltage, a desired motor speed (when the powereddevice 22 includes a motor), etc.) to the controller 58. Based on thisinformation, the controller 58 controls the boost converter 54 to supplythe necessary voltage to the powered device 22.

For example, normally, to reduce the speed of a motor, the input voltageto the motor is modulated through pulse-width modulation (PWM) to get alower average voltage, resulting in a lower speed. With the batterypower device 14 including the boost converter 54, because the boostconverter 54 provides the input voltage to the motor, the motor couldsend a request (e.g., through the powered device controller) to theboost converter 54 (e.g., to the controller 58) that it needs a giveninput voltage, speed, etc. (e.g., 75%). In such a case, rather thanbeing partially on (e.g., 75%) by pulse-width modulating the motorswitches/transistors, the motor would run “full on” but at a slowerspeed because the input voltage from the boost converter 54 is lower.This operation eliminates switching losses, heat, etc., associated withPWM of the motor.

Each battery pack 18 a, 18 b . . . 18 n can have any battery chemistrysuch as, for example, lead acid, Nickel-cadmium (“NiCd”), Nickel-MetalHydride (“NiMH”), Lithium (“Li”), Lithium-ion (“Li-ion”), anotherLithium-based chemistry or another rechargeable or nonrechargeablebattery chemistry. In the illustrated constructions, the battery packs18 a, 18 b . . . 18 n can have a battery chemistry of Li, Li-ion oranother Li-based chemistry and can supply an average discharge currentequal to or greater than approximately 20 A and generally up to 100 A ormore. For example, in the illustrated construction, the battery packs 18a, 18 b . . . 18 n can have a chemistry of Lithium Cobalt (“Li—Co”),Lithium Manganese (“Li—Mn”) Spinel or Li—Mn Nickel.

Each battery pack 18 a, 18 b . . . 18 n has a number of cellselectrically connected to provide a nominal voltage (e.g., 12 V, 18 V,20 V, 28 V, 36 V, 40 V, 56 V, 60 V, 120 V, etc.) for the pack 18, and,in the system 10, the battery packs 18 may have different nominalvoltages. Also, each battery pack 18 a, 18 b . . . 18 n has astate-of-charge (e.g., fully charged to end of discharge threshold),and, in the system 10, the battery packs 18 a, 18 b . . . 18 n may havedifferent states-of-charge. In addition, each battery pack 18 a, 18 b .. . 18 n has a capacity (e.g., 2 Ah, 4 Ah, etc.), and, in the system 10,the battery packs 18 a, 18 b . . . 18 n may have different capacities(based on different capacity cells, parallel-connected cells, etc.).

For example, one battery pack 18 a may have one nominal voltage (e.g.,18 V), while another battery pack 18 b has a different nominal voltage(e.g., 56 V). Also, one battery pack 18 a may have one state-of-charge(e.g., fully charged (100% SOC)) while another battery pack 18 b has adifferent SOC (e.g., 75% SOC). In this example, the system 10 operateswith the boost converter 54 to provide the set output voltage (e.g., 400V) with the input voltage provided by the 18 V battery pack 18 a and the56 V battery pack 18 b (and any other connected battery pack(s) 18),regardless of the relative states-of-charge of and capacity of thepack(s) battery packs 18 a, 18 b . . . 18 n.

FIG. 3 illustrates a charging arrangement for the multiple batterypacks, such as the battery packs 18 a, 18 b . . . 18 n shown in FIGS.1-2. It should be understood that the illustrated charging arrangementmay be used with or independently of the boost arrangement describedabove.

As shown in FIG. 3, for charging, the battery packs 18 a, 18 b . . . 18n are connected in parallel to charging circuitry 70. The chargingcircuitry 70 includes input terminals 74 connectable to a power source(not shown) to provide power the charging circuitry 70. In otherconstructions (not shown), the charging circuitry 70 may independentlyconnect the battery packs 18 a, 18 b . . . 18 n to the power source sothat each battery pack 18 a, 18 b . . . 18 n is independently andseparately charged.

The charging circuitry 70 may be supported in the housing assembly 26 ofthe device 14 so that the housing assembly 26 provides a unitarydischarging/charging carrier/platform. The housing assembly 26 may beinclude (see FIG. 1) a carrier portion 78 providing the support portions30 a, 30 b . . . 30 n and supporting the battery packs 18 a, 18 b . . .18 n as a unit. The carrier portion 78 with the battery packs 18 a, 18 b. . . 18 n can be separated from the remainder of the housing assembly26 and transported as a unit between different work sites, a charginglocation, etc. The carrier portion 78 may be constructed to be used withmultiple devices 14 (one shown) and may be interchanged between devices14.

During discharge operations, the battery packs 18 a, 18 b . . . 18 n areselectively connected in series in the circuit 34 to provide power atthe output terminals 50 (a “discharge” condition of the device 14). Whenthe battery packs 18 a, 18 b . . . 18 n are to be charged, the batterypacks 18 a, 18 b . . . 18 n are disconnected from the series connectionin the circuit 34 and connected in parallel (or independently) to thecharging circuitry 70 (a “charge” condition of the device 14). Anindicator 82 (see FIG. 1) provides an indication (visual, audible,tactile, combinations thereof, etc.) of the discharge/charge conditionof the device 14.

During charging, each battery pack 18 a, 18 b . . . 18 n is chargedindependently to avoid overcharging the higher SOC pack(s) 18 a, 18 b .. . 18 n while sufficiently charging the lower SOC pack(s) 18 a, 18 b .. . 18 n and to thereby bring the battery packs 18 a, 18 b . . . 18 n tosubstantially the same state of charge (given sufficient charging time).When a battery pack 18 a, 18 b . . . 18 n is fully charged, the batterypack 18 a, 18 b . . . 18 n may be disconnected from the power source toavoid overcharging.

During charging, the charging circuitry 70 may charge all battery packs18 a, 18 b . . . 18 n to the same capacity, rather than state-of-charge.The controller 58 communicates with and determines the capacity of thebattery packs 18 a, 18 b . . . 18 n. The charging circuitry 70 iscontrolled to only apply the capacity that the smallest capacity batterypack 18 a, 18 b . . . 18 n can receive, and all battery packs 18 a, 18 b. . . 18 n are charged to that capacity. During operation, theseries-connected battery packs 18 a, 18 b . . . 18 n are able to bedischarged to the same capacity, that of the lowest capacity batterypack 18 a, 18 b . . . 18 n. While runtime of the other battery packs 18a, 18 b . . . 18 n may be sacrificed with this arrangement, additionalcomponents for a balancing circuit, as described below, and theassociated costs are not required.

In order to provide selective series discharging along with parallelcharging, a switch arrangement (not shown) is provided to change theconnection of the battery packs 18 a, 18 b . . . 18 n as necessary fordischarging and charging. Generally, when the input terminals 74 areconnected to the power source, the output terminals 50 are disconnectedfrom the battery packs 18 a, 18 b . . . 18 n, and the battery packs 18a, 18 b . . . 18 n are connected in parallel. When the battery packs 18a, 18 b . . . 18 n are disconnected from the power source (e.g., bydisconnecting the input terminals 74 from the battery packs 18 a, 18 b .. . 18 n or by disconnecting the input terminals 74 from the powersource), the battery packs 18 a, 18 b . . . 18 n are connected in seriesand to the output terminals 50.

In some constructions, the controller 58 may control the switcharrangement based on information relating to the operation of the device14. The controller 58 may, for example, determine or receive a signalindicative of the connection status of the input terminals 74 relativeto the power source and/or the output terminals 50 relative to thepowered device 22 and control the switch arrangement accordingly. Asanother example, when the connected battery packs 18 a, 18 b . . . 18 nare discharged or disabled, the controller 58 may control the switcharrangement to the charge condition, regardless of the connection statusof the terminals 50, 74, until the battery packs 18 a, 18 b . . . 18 nare sufficiently charged for discharging operations.

In other constructions, the switching arrangement may be user actuated.An actuator may be connected to the switch arrangement and/or to thecontroller 58 to select the discharge condition or the chargedcondition. When the connected battery packs 18 a, 18 b . . . 18 n aredischarged or disabled, the user may be prevented from selecting thedischarge condition (e.g., by the controller 58) until the battery packs18 a, 18 b . . . 18 n are sufficiently charged for dischargingoperations.

FIG. 4 illustrates a balancing arrangement for the multiple batterypacks, such as the battery packs 18 a, 18 b . . . 18 n shown in FIGS.1-2, operable to rebalance the battery packs 18 a, 18 b . . . 18 n. Itshould be understood that the illustrated balancing arrangement may beused with or independently of the boost arrangement and/or the chargingarrangement described above.

A balancing circuit 86 is selectively connected to the battery packs 18a, 18 b . . . 18 n. The balancing circuit 86 may include an isolatedDC-DC power converter. The balancing circuit 86 operates to transferenergy from the high SOC battery pack(s) 18 a, 18 b . . . 18 n to thelow SOC battery pack(s) 18 a, 18 b . . . 18 n to balance the batterypacks 18 a, 18 b . . . 18 n (e.g., to within 10% state-of-charge).

The balancing circuit 86 may be selectively connected to anddisconnected from the battery packs 18 a, 18 b . . . 18 n. A switcharrangement (not shown) may be provided to operate the device 14 betweena “balancing” condition, in which the balancing circuit 86 is connectedto the battery packs 18 a, 18 b . . . 18 n and is operable to balancethe battery packs 18 a, 18 b . . . 18 n, and an “inoperable” condition,in which the balancing circuit 86 is not operable to balance the batterypacks 18 a, 18 b . . . 18 n (e.g., is disconnected).

The balancing circuit 86 would generally operate in the background(e.g., when the device 14 is not being discharged) and take some time(e.g., 15 minutes or more depending on the relative SOCs of the batterypacks 18 a, 18 b . . . 18 n) to balance the battery packs 18 a, 18 b . .. 18 n. Use of the balancing circuit 86 may improve the runtime of thesystem 10 by maximizing the energy available from all of the batterypacks 18 a, 18 b . . . 18 n when they are discharged in series.

The controller 58 may control operation of the balancing circuit 86(e.g., connection of the switch arrangement) based on informationrelating to the operation of the device 14. For example, the controller58 may determine non-use and/or predict periods of non-use (e.g.,off-peak hours) sufficient to operate the balancing circuit 86.

Because cells can discharge at higher rates than when charged, thebalancing circuit 86 can operate more quickly (fast balance) bydischarging the higher SOC battery pack(s) 18 a, 18 b . . . 18 n topower a charging circuit to charge the lower SOC battery pack(s) 18 a,18 b . . . 18 n. In such constructions, the balancing circuit 86includes a charging circuit (not shown) to be powered by the higher SOCbattery pack(s) 18 a, 18 b . . . 18 n.

FIGS. 5-6 illustrate a matrix power arrangement for a multi-phase motor90 in which energy is drawn from each battery pack 18 a, 18 b . . . 18 nbased on its state of charge and applied to the motor 90. In theillustrated construction, each battery pack 18 a, 18 b . . . 18 n hasits own connection to the motor 90. An inverter/bridge 94 a, 94 b . . .94 n is provided between each battery pack 18 a, 18 b . . . 18 n and themotor 90.

The battery packs 18 a, 18 b . . . 18 n are selectively connected acrosseach phase of the motor 90, and switching is operated to provide therequired energy to each phase of the motor 90. With the illustratedarrangement, the battery packs 18 a, 18 b . . . 18 n can be connected inseries and/or parallel combinations with the motor 90 to achieve thedesired runtime/power output with battery packs 18 a, 18 b . . . 18 nhaving different SOCs, capacities, nominal voltages, etc. Thearrangement may include a DC-DC converter bypass element for lower powerdissipation.

The operation, construction and charging of battery packs, includingthose with lithium-based battery cells, are described and illustrated inU.S. Pat. No. 7,157,882, issued Jan. 2, 2007; U.S. Pat. No. 7,253,585,issued Aug. 7, 2007; U.S. Pat. No. 7,176,654, issued Feb. 13, 2007; U.S.Pat. No. 7,589,500, issued Sep. 15, 2009; U.S. Pat. No. 7,714,538,issued May 11, 2010; and U.S. Pat. No. 7,425,816, issued Sep. 16, 2008;the entire contents of all of which are hereby incorporated byreference.

Thus, the invention provides, among other things, a battery powerdevice, system and method with series-connected battery packs. A boostconverter may convert the voltage of the series-connected battery packsto a set output voltage. The battery packs may be selectively connectedin series for discharging and in parallel for charging. A balancecircuit may transfer energy between the battery packs to balance thestates of charge of the battery packs. In a matrix power arrangement,multiple battery packs are selectively connected across each phase ofthe motor, and switching is operated to provide the required energy toeach phase of the motor.

One or more independent advantages and/or independent features may beset forth in the following claims:

What is claimed is:
 1. A power device comprising: a housing defining afirst support operable to support a first battery pack, and a secondsupport operable to support a second battery pack; charging circuitryelectrically connected to the first battery pack and the second batterypack in a parallel-type connection, the charging circuitry configured tosimultaneously charge the first battery pack and the second batterypack; discharge circuitry electrically connected to the first batterypack and the second battery pack, the discharge circuitry configured toelectrically connect the first battery pack and the second battery packin a series-type connection during a discharge; and a switch that iscontrolled to electrically disconnect one of the first battery pack andthe second battery pack from the series-type connection during thedischarge based on a state of the one of the first battery pack and thesecond battery pack, wherein the other of the first battery pack and thesecond battery pack is maintained in the series-type connection duringthe discharge.
 2. The power device of claim 1, wherein the chargingcircuitry includes a first switch to control charging of the firstbattery pack and a second switch to control charging of the secondbattery pack.
 3. The power device of claim 1, further comprising abalancing circuit configured to balance the first battery pack and thesecond battery pack during the discharge.
 4. The power device of claim1, wherein the charging circuitry determines a capacity of the firstbattery pack and a capacity of the second battery pack via acommunication with the first battery pack and the second battery pack.5. The power device of claim 1, wherein the first battery pack has afirst nominal voltage and the second battery pack has a second nominalvoltage different than the first nominal voltage.
 6. The power device ofclaim 1, wherein the first battery pack has a first capacity and thesecond battery pack has a second capacity different than the firstcapacity.
 7. The power device of claim 1, wherein the first battery packhas a first state of charge and the second battery pack has a secondstate of charge different than the first state of charge.
 8. The powerdevice of claim 1, wherein the first battery pack includes a batterypack housing removably supported by the first support, a battery cellsupported by the battery pack housing, and a terminal operable toconnect the battery cell to the charging circuitry.
 9. The power deviceof claim 1, wherein the second battery pack includes a battery packhousing removably supported by the second support, a battery cellsupported by the battery pack housing, and a terminal operable toconnect the battery cell to the charging circuitry.
 10. The power deviceof claim 1, wherein at least one selected from the group consisting ofthe first battery pack and the second battery pack is a power toolbattery pack.
 11. A method of operating a power device, the methodcomprising: receiving, via a first support, a first battery pack;receiving, via a second support, a second battery pack; electricallyconnecting the first battery pack to a charging circuitry in aparallel-type electrical connection; electrically connecting the secondbattery pack to the charging circuitry in a parallel-type electricalconnection; simultaneously charging, via the charging circuitry, thefirst battery pack and the second battery pack; electrically connectingthe first battery pack to the second battery pack in a series-typeelectrical connection during a discharge; electrically disconnecting oneof the first battery pack and the second battery pack from theseries-type connection during the discharge based on a state of the oneof the first battery pack and the second battery pack; and maintainingthe series-type connection during the discharge of the other of thefirst battery pack and the second battery pack.
 12. The method of claim11, further comprising determining, via a communication with the firstbattery pack and the second battery pack, a capacity of the firstbattery pack and a capacity of the second battery pack via thecommunication.
 13. The method of claim 12, wherein the first batterypack has a first state of charge and the second battery pack has asecond state of charge different than the first state of charge.
 14. Themethod of claim 11, further comprising disconnecting the first batterypack or the second battery pack when fully charged.
 15. The method ofclaim 11, wherein the first battery pack has a first nominal voltage andthe second battery pack has a second nominal voltage different than thefirst nominal voltage.
 16. The method of claim 11, wherein the firstbattery pack has a first capacity and the second battery pack has asecond capacity different than the first capacity.
 17. A systemcomprising: a first battery pack including a first battery pack housing,and a first battery cell contained within the housing; a second batterypack including a second battery pack housing, and a second battery cellcontained within the housing; and a power device including a powerdevice housing defining a first support operable to support the firstbattery pack housing, and a second support operable to support thesecond battery pack housing, a switch, and discharging circuitryelectrically connected to the first battery pack and the second batterypack, the discharge circuitry configured to electrically connect thefirst battery pack and the second battery pack in a series-typeconnection during a discharge; wherein during charging, the firstbattery pack and the second battery pack are connected in aparallel-type connection and the first battery pack and the secondbattery pack are charged simultaneously, wherein the switch iscontrolled to electrically disconnect one of the first battery pack andthe second battery pack from the series-type connection during thedischarge based on a state of the one of the first battery pack and thesecond battery pack, and wherein the other of the first battery pack andthe second battery pack is maintained in the series-type connectionduring the discharge.
 18. The system of claim 17, wherein the firstbattery pack has a first nominal voltage and the second battery pack hasa second nominal voltage different than the first nominal voltage. 19.The system of claim 17, wherein the first battery pack has a firstcapacity and the second battery pack has a second capacity differentthan the first capacity.
 20. The system of claim 17, wherein the firstbattery pack has a first state of charge and the second battery pack hasa second state of charge different than the first state of charge.